package com.lqk.demo.concurrencytools.threadpool;

import lombok.extern.slf4j.Slf4j;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author lqk
 * @date 2022/1/5 20:26
 */
@Slf4j
public class TestPool1 {
    public static void main(String[] args) {
        ThreadPool threadPool = new ThreadPool(1, 1000,
                TimeUnit.MILLISECONDS, 1, (queue, task)->{
            // 1) 死等
            queue.take();   // 死等
            // 2) 带超时等待
//            queue.offer(task, 1500, TimeUnit.MILLISECONDS);
            // 3) 让调用者放弃任务执行
//            log.debug("放弃{}", task);
            // 4) 让调用者抛出异常
//            throw new RuntimeException("任务执行失败: "+task);
            // 5) 让调用者自己执行任务
            task.run();
        });
        for (int i = 0; i < 4; i++) {
            int j = i;
            threadPool.execute(()->{
                try {
                    Thread.sleep(1000L);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                log.debug("打印 --> {}", j);
            });
        }
    }
}

@FunctionalInterface
interface RejectPolicy<T> {    // 拒绝策略
    void reject(BlockingQueue<T> queue, T task);
}

@Slf4j
class ThreadPool {
    // 任务队列
    private BlockingQueue<Runnable> taskQueue;
    // 线程集合
    private HashSet<Worker> workers = new HashSet();
    // 核心线程数
    private int coreSize;
    // 获取任务的超时时间
    private long timeout;
    // 时间单位
    private TimeUnit timeUnit;
    // 拒绝策略
    private RejectPolicy<Runnable> rejectPolicy;

    // 执行任务
    public void execute(Runnable task) {
        // 当任务数没有超过 coreSize 时, 直接交给 worker 对象执行
        // 如果任务数超过 coreSize 时, 加入任务队列暂存
        synchronized (workers){   // workers 成员变量是线程不安全的, 需要加入到同步代码块
            if (workers.size() < coreSize){
                Worker worker = new Worker(task);
                log.debug("新增 worker, {}, {}", worker, task);
                workers.add(worker);
                worker.start();
            } else {
//                taskQueue.put(task);
                taskQueue.tryPut(rejectPolicy, task);
            }
        }
    }
    
    public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapacity, RejectPolicy<Runnable> rejectPolicy) {
        this.coreSize = coreSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.taskQueue = new BlockingQueue<>(queueCapacity);
        this.rejectPolicy = rejectPolicy;
    }

    class Worker extends Thread {
        private Runnable task;

        public Worker(Runnable task) {
            this.task = task;
        }

        @Override
        public void run() {
            // 执行任务
            // 1) 当 task 不为空, 执行任务
            // 2) 当 task 执行完毕, 再接着从任务队列获取任务并执行
//            while (task != null || (task = taskQueue.take()) != null) {   // 没有超时时间
            while (task != null || (task = taskQueue.poll(timeout,timeUnit)) != null) { //有超时时间
                try{
                    log.debug("正在执行...{}", task);
                    task.run();
                } catch (Exception e){
                    e.printStackTrace();
                } finally {
                    task = null;
                }
            }
            synchronized (workers) {
                log.debug("worker被移除{}", this);
                workers.remove(this);
            }
        }
    }
}

@Slf4j
class BlockingQueue<T> {
    // 1. 任务队列
    private Deque<T> queue = new ArrayDeque<>();
    // 2. 锁
    private ReentrantLock lock = new ReentrantLock();
    // 3. 生产者条件变量
    private Condition fullWaitSet = lock.newCondition();
    // 4. 生产者条件变量
    private Condition emptyWaitSet = lock.newCondition();
    // 5. 容量
    private int capacity;

    public BlockingQueue(int capacity) {
        this.capacity = capacity;
    }

    // 带超时的阻塞获取
    public T poll(long timeout, TimeUnit unit) {
        lock.lock();
        try{
            // 将 timeout 统一转为 nanos(纳秒)
            long nanos = unit.toNanos(timeout);
            while (queue.isEmpty()){
                try {
                    if (nanos<=0){  // 表示超时
                        return null;
                    }
                    // 返回的是剩余时间, 防止虚假唤醒
                    nanos = emptyWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            // 获取队列头的元素并删除该元素
            T t = queue.removeFirst();
            fullWaitSet.signalAll();
            return t;
        }finally {
            lock.unlock();
        }
    }

    // 阻塞获取
    public T take() {
        lock.lock();
        try{
            while (queue.isEmpty()){
                try {
                    emptyWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            // 获取队列头的元素并删除该元素
            T t = queue.removeFirst();
            fullWaitSet.signalAll();
            return t;
        }finally {
            lock.unlock();
        }
    }
    // 阻塞添加
    public void put(T task) {
        lock.lock();
        try{
            while (queue.size() == capacity){
                try {
                    log.debug("等待加入任务队列... {}", task);
                    fullWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.debug("加入任务队列 {}", task);
            queue.addLast(task);
            emptyWaitSet.signalAll();
        }finally {
            lock.unlock();
        }
    }
    // 带超时时间的阻塞添加
    public boolean offer(T task, long timeout, TimeUnit unit) {
        lock.lock();
        try{
            long nanos = unit.toNanos(timeout);
            while (queue.size() == capacity){
                try {
                    log.debug("等待加入任务队列... {}", task);
                    if (nanos <= 0) {
                        return false;
                    }
                    nanos = fullWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.debug("加入任务队列 {}", task);
            queue.addLast(task);
            emptyWaitSet.signalAll();
            return true;
        }finally {
            lock.unlock();
        }
    }
    // 获取队列大小
    public int  size() {
        lock.lock();
        try {
            return queue.size();
        }finally {
            lock.unlock();
        }
    }
    //
    public void tryPut(RejectPolicy<T> rejectPolicy, T task){
        lock.lock();
        try {
            // 判断队列是否已满
            if (queue.size() == capacity){
                rejectPolicy.reject(this, task);
            } else {    // 有空闲
                log.debug("加入任务队列 {}", task);
                queue.addLast(task);
                emptyWaitSet.signalAll();
            }
        } finally {
            lock.unlock();
        }
    }
}